Thought I’d mention this on my thread for those looking for balance and strengthening equipment. No interest in it other than I like it. Anyway, I was concerned about hurting myself, tweaking my knee, on workout equipment which I have done before with balance boards. So prior to surgery, I bought a Step360 and love it. Each ring can be independently inflated or deflated with air creating a range of easy to extremely difficult workouts. I got the larger diameter size so I can easily put two feet on it at the same time. Currently, I have both rings almost flat so I can slowly work on balance.